How to convert centimeters to inches
The formula is simple: inches = centimeters ÷ 2.54. That is all this converter does, in either direction (inches to centimeters is centimeters = inches × 2.54). The reason the number 2.54 works so cleanly is that it is not an estimate. In 1959 the United States, the United Kingdom and the other English-speaking nations agreed to define the inch as exactly 25.4 millimeters. That single agreement tied the imperial system to the metric system with no approximation at all, which is why a conversion done here will match one done by an engineer, a tailor or an airline, digit for digit, apart from final rounding.
Centimeters-to-inches is probably the single most common length conversion in daily life. Product dimensions from European and Asian manufacturers are listed in centimeters, while American shoppers think in inches. Clothing and shoes, luggage sizes for airline cabins, furniture, picture frames, computer monitors, bicycle frames, aquarium sizes and baby stroller dimensions all cross this border constantly. Heights are another classic: a person who is 170 cm tall on a European form needs to become feet and inches on an American one — 170 cm is 66.93 inches, which is 5 feet and just under 7 inches.
Worked examples
- A suitcase: a cabin bag listed as 55 × 40 × 20 cm is 21.65 × 15.75 × 7.87 inches — now you can compare it to your airline's inch-based size limits.
- A picture frame: a 30 × 40 cm print is 11.81 × 15.75 inches, so the common American 12 × 16 inch frame fits with a small border.
- A laptop screen: screens are sold by diagonal inches, so a screen described as 39.6 cm across is a 15.6-inch laptop.
- Going the other way: a 65-inch television is 65 × 2.54 = 165.1 cm across the diagonal.
CM to inches conversion table
For quick reference — the values people look up most often:
| Centimeters | Inches | Centimeters | Inches |
|---|---|---|---|
| 1 cm | 0.3937 in | 30 cm | 11.81 in |
| 2 cm | 0.7874 in | 40 cm | 15.75 in |
| 5 cm | 1.9685 in | 50 cm | 19.69 in |
| 10 cm | 3.9370 in | 60 cm | 23.62 in |
| 15 cm | 5.9055 in | 80 cm | 31.50 in |
| 20 cm | 7.8740 in | 100 cm | 39.37 in |
| 25 cm | 9.8425 in | 180 cm | 70.87 in |
A memory shortcut: since 2.54 is close to 2.5, multiplying centimeters by 0.4 gives a rough inch figure that is within about 2% — good enough for guessing whether furniture will fit through a door, but use the converter above when the fit is tight.
Fractions of an inch
American tape measures and rulers divide inches into fractions — halves, quarters, eighths and sixteenths — rather than decimals. To read a decimal result as a fraction, look at the part after the decimal point: 0.25 is ¼, 0.5 is ½, 0.75 is ¾, and each eighth is 0.125. So 11.81 inches is, for most practical purposes, 11⅞ inches (11.875). For sewing, woodworking and most household jobs, rounding to the nearest eighth of an inch is normal and expected; nobody's bookshelf needs laboratory precision. When something must fit exactly — a screen protector, a machine part, a replacement panel — keep the full decimal figure this converter gives you and compare it against the manufacturer's own specification.
Frequently asked questions
How many centimeters are in one inch?
Exactly 2.54 — by international definition since 1959.
How do I convert cm to inches by hand?
Divide by 2.54. For example, 30 ÷ 2.54 = 11.81 inches. Reverse the process (multiply by 2.54) to turn inches back into centimeters.
What is 170 cm in feet and inches?
170 ÷ 2.54 = 66.93 inches, which is 5 feet (60 inches) plus 6.93 inches — about 5′7″.
Is 10 cm exactly 4 inches?
Not quite: 10 cm is 3.937 inches. Four inches is 10.16 cm. The difference is small but real, and it matters for tight fits.
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